1. Field of the Invention
The present invention relates to an electron emission device, and in particular, to an electron emission display that reduces a resistance by widening an effective width of driving electrodes, and improves a shape of the driving electrodes to achieve a high resolution display screen.
2. Description of Related Art
In general, an electron emission element can be classified, depending upon the kinds of electron sources, into a hot cathode type or a cold cathode type.
Among the cold cathode type of electron emission elements, there are a field emitter array (FEA) type, a surface conduction emission (SCE) type, a metal-insulator-metal (MIM) type, and a metal-insulator-semiconductor (MIS) type.
The FEA type of electron emission element includes electron emission regions, and cathode and gate electrodes that are used as the driving electrodes for controlling emission of electrons from electron emission regions. The electron emission regions are formed with a material having a low work function and/or a high aspect ratio. For instance, the electron emission regions are formed with a sharp-pointed tip structure that is formed with molybdenum (Mo) or silicon (Si), or a carbonaceous material such as carbon nanotube (CNT), graphite, and diamond-like carbon (DLC). With the usage of such a material for the electron emission regions, when an electric field is applied to the electron emission regions under a vacuum atmosphere (or vacuum state), electrons are easily emitted from the electron emission regions.
Arrays of electron emission elements are arranged on a first substrate to form an electron emission device. A light emission unit is formed on a second substrate with phosphor layers and an anode electrode, and is assembled with the first substrate to thereby form an electron emission display.
In the electron emission device, the plurality of driving electrodes functioning as the scanning and data electrodes are provided together with the electron emission regions to control the on/off of electron emission for respective pixels due to the operation of the electron emission regions and the driving electrodes, and also to control the amount of electrons emitted from the electron emission regions. The electrons emitted from the electron emission regions excite the phosphor layers to thereby emit light or display images.
With the above described electron emission device, an unstable driving voltage may be applied to an electrode (for convenience, hereinafter referred to as the “first electrode”) electrically connected to the electron emission regions to supply the electric currents required for the electron emission, or the voltage applied to the electron emission regions may be differentiated due to a voltage drop of the first electrode. In this case, the emission characteristics of the electron emission regions become non-uniform so that light emission uniformity per respective pixels is deteriorated.
Accordingly, in order to solve such a problem, as shown in FIG. 6, opening portions 13 are internally formed at first electrodes 11 to expose a surface of a first substrate 9, and isolation electrodes 15 are formed within respective opening portions 13. Resistance layers 17 are formed between the first electrodes 11 and the isolation electrodes 15 at both ends of the isolation electrodes 15 to make the emission characteristics of electron emission regions 19 more uniform.
However, with the above-described structure of the first electrodes 11, the widths d1 and d2 of the first electrodes 11, the widths d3 and d4 of the respective resistance layers 17, and the width d5 of the isolation electrodes 15 should be contained in the width direction of the first electrodes 11 within the pixel areas where the electron emission regions 19 are located. Therefore, the effective width of the first electrodes 11 that can practically serve for the electric current flow is only the sum of d1 and d2.
Accordingly, with the above-structured electron emission device, a voltage drop inevitably occurs due to the increase in resistance pursuant to the reduction in an effective width. In the case that the effective width is enlarged to lower the resistance, it is difficult to achieve a high resolution display screen due to the enlargement in the width of the first electrodes.